* registers sql metrics for unified storage and removes single quotes from postgres connection string format
* uses db logger
* only register US sql metrics when connecting to another postgres or mysql db
* use engine
Storage Server: avoid incorrect parsing of connection string
In storage server, a connection string is generated to connect to the
backing database. In case of Postgres, we were generating the string
like `"user=grafana pass= host=postgres.example port=4567"`.
This triggered an edge case in `pq` (the go postgres driver) to parse
`pass` to be equal to `host=postgres.example`, and host being reset to
default value.
Using single quotes in the connection string fixed this.
Signed-off-by: Prem Kumar <prem.saraswat@grafana.com>